Browsing by Author "Melo, Maria M. P."
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- Amostragem inteligente como abordagem expedita para monitorização de iões de metal em águas naturais: projeto Aqua_SmartPublication . Pereira, Mafalda G.; Melo, Maria M. P.; Mesquita, Raquel B. R.; Ribas, Tânia C. F.; Machado, Ana; Rangel, António O. S. S.
- Amostragem inteligente como abordagem expedita para monitorização de iões de metal em águas naturais: projeto Aqua_SmartPublication . Pereira, Mafalda G.; Melo, Maria M. P.; Mesquita, Raquel B. R.; Ribas, Tânia; Machado, Ana; Rangel, António O. S. S.O projeto Aqua_Smart (FCT ref. 2022.08713.PTDC) foi concebido com o objetivo de desenvolver um conceito de amostragem inteligente integrada numa monitorização automática do teor de iões potencialmente tóxicos em águas, permitindo monitorizar alterações ambientais que podem ter impacto na saúde pública, promovendo uma abordagem “One Health”. Neste trabalho reporta-se a utilização de uma PIM como suporte de troca aniónica, explorando a tendência para formar cloro complexos de cobalto, permitindo a determinação deste ião. Neste enquadramento, tornou-se relevante combinar com a determinação do teor em anião cloreto, usando um reagente colorimétrico de baixa toxicidade.
- Assessment of collagen content in fish skin: development of a flow analysis method for hydroxyproline determinationPublication . Melo, Maria M. P.; Mesquita, Raquel B. R.; Coscueta, Ezequiel R.; Pintado, Manuela E.; Rangel, António O. S. S.This work describes the development of a flow injection method to determine hydroxyproline (HYP), one of collagen's most abundant amino acids. Collagen is a protein with several applications and high nutritional value. Evaluating the feasibility of using collagen from fish skin over its mammalian source is essential. The determination of HYP requires the pre-treatment and hydrolysis of the fish skin to break down collagen into its amino acids, and the HYP value quantified relates to the collagen content. The determination was based on the HYP oxidation with permanganate in an alkaline medium and the consequent decrease of colour intensity registered. Under optimal conditions, the developed method enables the determination of the HYP within the dynamic range of 23.8 to 500 mg L −1, with a limit of detection (LOD) of 2.6 mg L −1 and a limit of quantification (LOQ) of 23.8 mg L −1. Different samples were processed, and the digests were analysed by the proposed method and with the conventional procedure with good correlation (relative error < 7%). Moreover, the analyte quantification is performed faster, simpler, and more accurately, with less toxic solutions. The reproducibility of the developed method was also evaluated by calculating the relative standard deviation of the calibration curve slope (RSD < 1%).
- Collagen determination in fish skin: development of a flow analysis system for quantification of hydroxyprolinePublication . Melo, Maria M. P.; Coscueta, Ezequiel R.; Pintado, Manuela E.; Mesquita, Raquel B. R.; Rangel, António O. S. S.
- Collagen determination in fish skin: development of a flow analysis system for quantification of hydroxyprolinePublication . Melo, Maria M. P.; Coscueta, Ezequiel R.; Pintado, Manuela E.; Mesquita, Raquel B. R.; Rangel, António O. S. S.Collagen is a protein with various applications, namely in the food area. It has valuable properties, since it is a polymer with weak antigenicity, low toxicity, and high nutritional value, among other features [1]. Its extraction from mammalian sources, i.e., bovines, is decreasing due to health and environmental problems and, therefore, fish have become a good alternative for collagen resources [2].One way to quantify the collagen present in fish skin, in order to obtain high-value fractions, is the determination of hydroxyproline (HYP), an amino acid highly present in collagen [1]. The determination of HYP from fish skin requires the hydrolysis of a skin section, to break collagen in its amino acids and the HYP value quantified is compared to the amount present in pure collagen, studied previously (38 μg of HYP per mg of pure collagen). The quantification of HYP is based on its oxidation combined with the reaction with DAB (dimethylaminobenzaldehyde) that forms a chromophore-coloured product. The HYP can then be correlated with the spectrophotometric measurement of this coloured product. A batchwise approach was performed to study the best reaction conditions, namely different reagents, heating times and proportions.The main goal of this work is to develop an automated flow injection analysis (FIA) method, to miniaturize the determination of HYP. Several operation parameters like flow rates, number of channels, tube diameters and lengths of reactors will be studied to optimize the developed FIA method.
- Design and assembly of a μPAD for zinc determination in children’s saliva samplesPublication . Melo, Maria M. P.; Rangel, António O. S. S.; Mesquita, Raquel B. R.Anticipating health issues with frequent monitoring as a strategy requires easy-to-use, real-time, and accurate analytical devices. Paper-based sensors coupled with the easy non-invasive collection of biological fluids, like saliva, make this combination particularly well-suited for frequent monitoring of infants’ health. Saliva samples contain biomarkers that can provide the early detection of medical conditions, as it is the case of zinc. Regarding newborn babies and children, zinc deficiency can cause a decline in nutrition status, as well as compromise the child’s cognitive behaviour. As so, zinc determination in saliva is crucial to assess its levels and the consequent child’s state of development. The main goal is to develop a microfluidic paper-based analytical device (?PAD) for rapid and on-site zinc quantification. This innovative ?PAD methodology is portable and simple while providing low-cost analysis. Additionally, it is environmentally friendly, as it uses small amounts of reagents and samples, resulting in low waste production. For zinc determination, each device is fabricated by stacking two layers of filter paper discs (9.5 mm of diameter) that are aligned and inserted into a laminated plastic pouch, with 3 mm holes to insert the standard/sample solutions. The top layer contains the reagent (dithizone), while the bottom layer contains sodium hydroxide to ensure the reaction pH. When the standard/sample is loaded, a coloured pink complex is formed, and the intensity values are used to calculate the absorbance, establishing a linear correlation with zinc concentration. After validation by comparing to a reference procedure, the stability of the ?PAD will be assessed under several storage conditions, and it will be applied to children’s saliva samples.
- Design of a disposable µPAD for on-hand quantification of urinary creatininePublication . Melo, Maria M. P.; Rangel, António O. S. S.; Mesquita, Raquel B. R.In this work, a new microfluidic paper-based analytical device (μPAD) was developed for on-hand creatinine quantification in urine samples. This is clinically significant since creatinine monitorization in urine is an indicator of health condition, as kidney-failure [1]. When compared with conventional methods, this innovative μPAD approach is more accessible, portable, providing low-cost analysis and applicable to non-invasive biological fluids [2]. Additionally, the μPAD is environmentally friendly, as it uses small amounts of reagents, results in low waste production, and is disposal by incineration. The developed μPAD configuration consisted in two layers of filter paper discs (9.5 mm of diameter) staked into a hydrophilic unit and aligned into a laminated plastic pouch (hydrophobic zone), with 3 mm holes for the standard/sample insertion. The top layer served as a reservoir and the bottom layer contained the reagent (alkaline picrate). After the standard/sample loading, creatinine reacts with picric acid in alkaline conditions, forming an orange/red complex. The colour was registered by scanning the μPAD and the image processed in ImageJ software to obtain the colour intensity values then used to calculate the absorbance. A linear correlation was established between the creatinine concentration and the calculated absorbance values. The μPAD operational parameters were studied to attain the best sensitivity (calibration curve slope) for creatinine determination within the dynamic range of 2.20 - 35.0 mg/dL with a limit of detection (LOD) of 0.66 mg/dL and a limit of quantification (LOQ) of 2.2 mg/dL. Finally, the method was validated by analysing several urine samples with the developed μPAD and comparing the results with a comparative batchwise process, and it was demonstrated that there were no statistically significant differences between them.
- Disposable microfluidic paper-based device for on-site quantification of urinary creatininePublication . Melo, Maria M. P.; Machado, Ana; Rangel, António O. S. S.; Mesquita, Raquel B. R.In this work, a new microfluidic paper-based analytical device (µPAD) was developed for on-hand creatinine quantification in urine samples. When compared to conventional methods, this innovative paper device is more accessible and portable, it provides low-cost analysis (cost of consumables of 40 cents), and it is applicable to non-invasive biological fluids. Furthermore, the paper-based approach is used within an environmentally friendly assembly with no need for wax printing and small amounts of reagents resulting in low waste production and easy disposal by incineration. Its assembly method includes cutting paper discs arranged into several reading units within a plastic pouch, enabling effective creatinine quantification with accuracy based on a vertical flow approach. The method is based on the colourimetric reaction between creatinine and alkaline picric acid, where the solution colour changes from yellow to orange/red. Under optimal conditions, the developed method allowed creatinine quantification in the dynamic range of 2.20–35.0 mg/dL, with a limit of detection (LOD) of 0.66 mg/dL and a limit of quantification (LOQ) of 2.20 mg/dL. The colour intensity developed was processed in ImageJ software, based on digital image scanning, performed in 20 min (up to 4 h) after the sample insertion. The device is stable for up to one week when stored in a vacuum at 4 °C. The method was validated by comparing the results with a batch-wise procedure, where there were no statistically significant differences between both methods.
- Flow analysis method for hydroxyproline determination to assess collagen content in fish skinPublication . Melo, Maria M. P.; Mesquita, Raquel B. R.; Coscueta, Ezequiel R.; Pintado, Manuela E.; Rangel, António O. S. S.Collagen is a protein with several applications, with weak antigenicity, low toxicity, and high nutritional value. Usually, it is extracted from bovine skin, but a project was designed proposing an alternative to extract collagen from fish skin. This alternative was tested by assessing the collagen content in fish skin based on the determination of hydroxyproline (HYP), one of the most abundant amino acid present in collagen (Sotelo et al., 2016). Therefore, the determination of HYP requires the hydrolysis of the fish skin, to break collagen in its amino acids, and the HYP value quantified relates to the collagen content. This was previously assessed to be 38 μg of HYP per mg of pure collagen. In this context, the aim of the described work was to develop an automatic method based on flow injection analysis approach to determine HYP. The determination was based on the redox reaction with permanganate (Farokhi et al., 2002) and the consequent decrease of colour intensity registered. The best conditions for the determination were studied, namely, reagent concentration, sample volume, flow rate and reaction time. The developed method enables the determination of the HYP in a faster, simpler and accurate way, with less toxic solutions.
- Metal ions retention: polymer inclusion membrane as sorbent materialPublication . Melo, Maria M. P.; Mesquita, Raquel B. R.; Ribas, Tânia C. F.; Rangel, António O. S. S.